Control method and preparation method of quenching deformation of die castings

Abstract

The invention discloses a control method and a preparation method for quenching deformation of a die-casting. The control method comprises the following steps: performing zone cooling on a die-casting after solution treatment to obtain an actual deformation of the die-casting after cooling; establishing a simulation model to obtain a simulated deformation of the die-casting; comparing the simulated deformation with the actual deformation; simulating and optimizing a zone quenching and cooling process of the die-casting based on a revised model; performing a quenching and cooling test on the die-casting based on the simulated and optimized zone quenching and cooling process, and revising the zone quenching and cooling process based on a result of a cooling rate; performing zone quenching and cooling on the die-casting based on the revised zone quenching and cooling process, and obtaining a revised deformation of the die-casting after quenching and cooling, and comparing the revised deformation with design dimension data of the die-casting; performing a constraint simulation analysis on a position where the deformation degree is greater than 1 mm to obtain a constraint mode with the minimum deformation degree.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep processing of aluminum alloy materials, and particularly relates to a method for controlling quenching deformation of large thin-walled die castings and a method for preparing large thin-walled die castings comprising the control method. Background Art

[0002] Large, thin-walled die castings, such as automotive longitudinal beams, can experience significant deformation during the quenching process after solution treatment. Existing techniques typically employ quenching fixtures to constrain the deformation and control the casting's deformation.

[0003] For example, patent publication number CN105838860A discloses a heat treatment method for front shock absorbers of new energy vehicles, comprising the following steps: heat treatment, hanging, melting, cooling, air cooling, and heat preservation. This patent targets the deformation points of the product and produces a dedicated heat treatment rack to improve the deformation phenomenon that occurs during the heat treatment process. This also reduces or eliminates the need for post-heat treatment shape correction, which has the advantage of improving production efficiency. However, this patent does not involve specific quenching processes and quenching details. Due to the small size of the casting, the designed quenching tooling is too simple and cannot be applied to large, thin-walled die castings.

[0004] For example, patent publication number CN213416958U discloses a heat treatment deformation control jig for aluminum shock towers used in new energy vehicles. This jig controls deformation during the heat treatment process, improving the tower's precision; meeting the tower's connection requirements, reducing scrap rates, eliminating the need for reshaping steps, and lowering production costs. However, the patent covers the specific structure of the heat treatment deformation control jig for the aluminum shock tower, but does not address how to control the aluminum shock tower's deformation through specific quenching processes, placement methods, and the specific constraints imposed by the tooling on the casting.

[0005] For example, patent publication number CN112338003B discloses a method for correcting deformation during manufacturing of thin-walled aluminum-magnesium alloy cabins. The method primarily uses thermal simulation and creep tests to determine the material deformation and creep constitutive relationships of cabin components. Internal support fixtures are then designed and manufactured to provide adjustable constraints on the deformation position of cabin components. However, due to the relatively simple and regular structure of the castings, the quenching fixtures designed in this patent are overly simple and rely entirely on the fixtures to control deformation. For large, complex, thin-walled die-castings, the synergistic effects of the quenching process and quenching fixtures must be considered. Therefore, this invention has certain limitations and is not suitable for controlling quenching deformation of large, thin-walled die-castings.

[0006] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of the present invention. In the absence of clear evidence showing that the above content has been disclosed before the application date of the present invention, the above background technology should not be used to evaluate the novelty and creativity of the present invention. Summary of the Invention

[0007] In view of this, in order to overcome the defects of the prior art, the purpose of the present invention is to provide a method for controlling quenching deformation of large thin-walled die castings, so as to reduce the deformation of the die castings during the quenching cooling process after solution treatment.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for controlling quenching deformation of large thin-walled die castings comprises the following steps:

[0010] The die castings after solution treatment are cooled in different zones, including the division of the surface area of the die castings and the use of cooling media with different parameters for different zones, and the actual deformation of the die castings after quenching and cooling is obtained;

[0011] Establish a simulation model and perform partitioned quenching and cooling simulation to obtain the simulated deformation of the die casting;

[0012] Comparing the simulated deformation with the actual deformation, and modifying the model according to the comparison result to ensure that the difference between the simulated deformation and the actual deformation is less than or equal to 0.2 mm;

[0013] Based on the revised model, the zoned quenching cooling process of the die casting was simulated and optimized. After the simulation optimization, the difference in the simulated cooling rate between different areas of the die casting was ensured to be within 5°C / s.

[0014] Based on the simulated and optimized partitioned quenching and cooling process, a quenching and cooling test was conducted on the die casting. Multiple thermocouples were set up in each partition. The cooling rate of each area of the die casting was monitored based on the thermocouple measurement results. The partitioned quenching and cooling process was modified based on the cooling rate results to ensure that the actual cooling rate difference between different areas of the die casting was within 5°C / s.

[0015] Performing zone quenching and cooling on the die casting based on the revised zone quenching and cooling process, and obtaining a revised deformation of the die casting after quenching and cooling, comparing the revised deformation with the design dimensional data of the die casting, and marking locations where the deformation is greater than 1 mm;

[0016] Based on the modified partitioned quenching and cooling process model, constraint simulation analysis was performed on locations where the deformation degree was greater than 1 mm, and the constraint method with the minimum deformation degree was obtained.

[0017] According to some preferred embodiments of the present invention, the surface areas of the die casting are divided into: the area with reinforcing ribs or wall thickness greater than 3 mm is divided into the first area, and the area without reinforcing ribs and wall thickness less than or equal to 3 mm is divided into the second area.

[0018] According to some preferred embodiments of the present invention, cooling the divided zones using cooling media with different parameters involves: cooling the first zone with a first medium, and cooling the second zone with a second medium; the heat transfer coefficient between the first medium and the first zone is 200-2000 W / (m2·K), and the heat transfer coefficient between the second medium and the second zone is 100-200 W / (m2·K). The heat transfer coefficient in this invention is the convective heat transfer coefficient that characterizes the heat transfer capacity between a fluid (cooling medium) and a solid surface (die casting).

[0019] According to some preferred implementation aspects of the present invention, the simulation optimization of the zoned quenching cooling process of the die-casting is as follows: the first region and the corresponding cooling medium are optimized, and the heat transfer coefficient between the region where the area of the reinforcing ribs accounts for more than 10% of the unit projected area and the cooling medium is 1000-2000W / (㎡·K); the heat transfer coefficient between the region where the area of the reinforcing ribs accounts for 3-10% of the unit projected area and the cooling medium is 600-1000W / (㎡·K); the heat transfer coefficient between the region where there are no reinforcing ribs or the area of the reinforcing ribs accounts for less than 3% of the unit projected area and the cooling medium is 200-600W / (㎡·K). The projection plane corresponding to the projection in the present invention is perpendicular to the direction of the cooling medium ejection, that is, the direction of the projection light is the direction of the cooling medium ejection. The larger the proportion of the reinforcing ribs or the thicker the corresponding wall thickness, the greater the heat transfer coefficient between the cooling medium and the area, thereby achieving a better cooling effect and accelerating cooling; conversely, the smaller the proportion of the reinforcing ribs or the thinner the corresponding wall thickness, the smaller the heat transfer coefficient between the cooling medium and the area, thereby keeping the area cooling slower, so that the cooling rate between different areas remains consistent or the difference in cooling rate is as small as possible.

[0020] According to some preferred embodiments of the present invention, the first medium and / or the second medium are fluid cooling media with different characteristics, and the heat transfer coefficient between the cooling medium and the die casting is controlled by adjusting the fluid flow rate or pressure.

[0021] According to some preferred implementation aspects of the present invention, the model is corrected according to the comparison results as follows: if the difference between the simulated deformation and the actual deformation is less than or equal to 0.2 mm, the model meets the simulation accuracy requirements and no further correction is required; if the difference between the simulated deformation and the actual deformation is greater than 0.2 mm, the model needs to be further corrected until the difference between the two is less than or equal to 0.2 mm.

[0022] According to some preferred embodiments of the present invention, the partitioned quenching cooling process is corrected based on the cooling rate results as follows: if the average difference in cooling rate between different regions is less than or equal to 5°C / s, the model meets the simulation accuracy requirements and no further correction is required; if the average difference in cooling rate between different regions is greater than 5°C / s, the model needs to be further corrected until the average difference in cooling rate between different regions is less than or equal to 5°C / s.

[0023] According to some preferred embodiments of the present invention, the average difference in cooling rate between different regions of a die casting with higher dimensional accuracy is within 2° C. / s.

[0024] According to some preferred implementation aspects of the present invention, the constraint simulation is: performing Y (width direction), Z (height direction) and YZ direction constraint simulation on positions where the deformation degree is greater than 1 mm.

[0025] According to some preferred implementation aspects of the present invention, the steps also include: finding the three constraint methods with the smallest deformation after the constraint simulation analysis, and performing quenching and cooling tests based on the three constraint methods with the smallest deformation and the revised partitioned quenching and cooling process, and selecting the constraint method with the smallest deformation of the die-casting and the revised partitioned quenching and cooling process as the optimal control method.

[0026] According to some preferred embodiments of the present invention, the solution treatment is to keep the die casting at 480-530° C. for 1-6 hours.

[0027] According to some preferred embodiments of the present invention, during the solution treatment and quenching cooling process, the die casting is continuously constrained at both ends of the die casting in the longitudinal direction, and the constraint direction is inward in the longitudinal direction of the die casting. The longitudinal direction of the die casting is the X direction.

[0028] The present invention also provides a method for preparing large thin-walled die castings, which includes the steps of the method for controlling quenching deformation of large thin-walled die castings as described above, and can effectively reduce the deformation of the castings during the quenching process after solution treatment.

[0029] Due to the adoption of the above technical solution, compared with the existing technology, the benefits of the present invention are: the control method of quenching deformation of large thin-walled die-castings of the present invention is based on the idea of zoning cooling, and the simulation model is verified, optimized and corrected based on actual data to obtain the optimal zoning cooling parameters and constraint process, which can effectively reduce the deformation of die-castings during the quenching cooling process after solution treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 This is a schematic diagram of the first area and the second area divided in an embodiment of the present invention; in the figure, dark red represents the first area, and light purple represents the second area;

[0032] Figure 2 This is a photo of a die-cast part after quenching treatment in an embodiment of the present invention; points A and B in the photo are two locations where the deformation is greater than 1 mm;

[0033] Figure 3 This is a simulation diagram after quenching treatment in step S2 of an embodiment of the present invention;

[0034] Figure 4 This is a simulation diagram of the die casting after being processed based on the optimal processing technology in step S8 of an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0036] The die-casting of the present invention is a casting with a length greater than 1000mm, a wall thickness that is basically less than or equal to 3mm, a wall thickness greater than 3mm in some parts due to the addition of reinforcing ribs, and an overall length / height or width ratio greater than 10, such as an automobile longitudinal beam. The present invention adopts the idea of zoning cooling to ensure that the overall cooling rate of large thin-walled die-castings during the quenching process is basically consistent, thereby minimizing the deformation of the castings. On this basis, the zoning cooling parameters and constraint methods are designed and optimized to effectively constrain the quenching process of the die-castings, so as to further reduce the deformation of the castings, thereby effectively controlling the quenching deformation that may exist during the quenching process of the castings. The method for controlling quenching deformation of large thin-walled die-castings of the present invention comprises the following steps:

[0037] Step S1, performing zone cooling on the die casting after solution treatment, including dividing the surface area of the die casting and cooling different divided areas with cooling media of different parameters, and obtaining the actual deformation of the die casting after cooling.

[0038] Solution treatment involves holding the die casting at 480-530°C for 1-6 hours. During solution treatment and the entire quenching and cooling process, the die casting is continuously restrained at both ends along its length, with the restraint direction pointing inward. The die casting's length is defined as the X direction, its width as the Y direction, and its height as the Z direction.

[0039] In this step, the area on the surface of the die casting with reinforcing ribs or a wall thickness greater than 3 mm is divided into the first area, and the area on the surface without reinforcing ribs and with a wall thickness less than or equal to 3 mm is divided into the second area.

[0040] Different cooling media with different parameters are used for cooling the different zones: the first zone is cooled by the first medium, and the second zone is cooled by the second medium. The heat transfer coefficient between the first medium and the first zone is 200-2000 W / (㎡·K), and the heat transfer coefficient between the second medium and the second zone is 100-200 W / (㎡·K). The heat transfer coefficient is the convective heat transfer coefficient that characterizes the heat transfer capacity between the fluid (cooling medium) and the solid surface (die casting).

[0041] Preferably, the first medium and the second medium are air, and the heat transfer coefficient between the medium and the die casting is controlled by adjusting the flow rate or pressure of the air.

[0042] Step S2: Establish a simulation model and perform a partitioned quenching and cooling simulation based on the parameters of step S1 to obtain a simulated deformation of the die casting.

[0043] Step S3: Compare the simulated deformation with the actual deformation, and modify the model according to the comparison result to ensure that the difference between the simulated deformation and the actual deformation is less than or equal to 0.2 mm.

[0044] Specifically, if the difference between the simulated deformation and the actual deformation is less than or equal to 0.2 mm, the model meets the simulation accuracy requirements and no further correction is required; if the difference between the simulated deformation and the actual deformation is greater than 0.2 mm, the model needs to be further corrected until the difference between the two is less than or equal to 0.2 mm.

[0045] Step S4: Based on the modified model, the zoned quenching cooling process of the die casting is simulated and optimized, and after the simulation optimization, the difference in simulated cooling rate between different areas of the die casting is ensured to be within 5° C. / s.

[0046] Specifically, the simulation optimization optimizes the first region and the corresponding cooling medium. For regions where the area of the reinforcement ribs per unit projected area exceeds 10%, the heat transfer coefficient between the region and the cooling medium is 1000-2000W / (㎡·K); for regions where the area of the reinforcement ribs per unit projected area exceeds 3-10%, the heat transfer coefficient between the region and the cooling medium is 600-1000W / (㎡·K); and for regions where there are no reinforcement ribs or the area of the reinforcement ribs per unit projected area exceeds 3%, the heat transfer coefficient between the region and the cooling medium is 200-600W / (㎡·K). The projection plane corresponding to the projection is perpendicular to the direction of the cooling medium ejection, that is, the direction of the projection light is the direction of the cooling medium ejection. The larger the proportion of the reinforcing ribs or the thicker the corresponding wall thickness, the greater the heat transfer coefficient between the cooling medium and the area, thereby achieving a better cooling effect and accelerating cooling; conversely, the smaller the proportion of the reinforcing ribs or the thinner the corresponding wall thickness, the smaller the heat transfer coefficient between the cooling medium and the area, thereby keeping the area cooling slower, so that the cooling rate between different areas remains consistent or the difference in cooling rate is as small as possible.

[0047] Step S5: Perform a quenching and cooling test on the die casting based on the partitioned quenching and cooling process after simulation optimization. Multiple thermocouples are set in each partition. The cooling rate of each area of the die casting is monitored based on the measurement results of the thermocouples. The partitioned quenching and cooling process is corrected based on the cooling rate results to ensure that the actual cooling rate difference between different areas of the die casting is within 5°C / s.

[0048] Specifically, if the average difference in cooling rate between different regions is less than or equal to 5°C / s, the model meets the simulation accuracy requirements and no further correction is required; if the average difference in cooling rate between different regions is greater than 5°C / s, the model needs to be further corrected until the average difference in cooling rate between different regions is less than or equal to 5°C / s.

[0049] More preferably, for die castings requiring higher dimensional accuracy, the average difference in cooling rate between different regions of the die castings needs to be within 2° C. / s.

[0050] In some embodiments, a plurality of thermocouples are provided in each partition, and the plurality of thermocouples are dispersed in each area.

[0051] Step S6: Perform zone quenching and cooling on the die casting based on the corrected zone quenching and cooling process, and obtain the corrected deformation of the die casting after quenching and cooling. Compare the corrected deformation with the target design dimension data of the die casting, and mark the position where the deformation degree is greater than 1 mm.

[0052] Step S7: Based on the modified model of the zoned quenching and cooling process, a constraint simulation analysis is performed on the positions where the deformation degree is greater than 1 mm to obtain a constraint method with the minimum deformation degree.

[0053] Constraint simulation is to perform Y (width direction), Z (height direction) and YZ direction constraint simulation for positions with deformation greater than 1mm.

[0054] Optionally, step S8 is further included, wherein the three constraint methods with the smallest deformation are identified after the constraint simulation analysis, and the die casting is quenched and cooled based on the three constraint methods with the smallest deformation and the revised zoned quenching and cooling process. The constraint method with the smallest deformation of the die casting and the revised zoned quenching and cooling process are selected as the optimal control method. Although step S5 has obtained the revised cooling process and step S7 has obtained the optimal constraint method, there may still be certain error fluctuations, and actual experiments are required to obtain the optimal quenching process.

[0055] The method for preparing large thin-walled die castings, including the above steps of the method for controlling the quenching deformation of large thin-walled die castings, can effectively reduce the deformation of the die castings during the quenching process after solution treatment.

[0056] Example: The large thin-walled die casting in this example is an automobile longitudinal beam die casting, made of Al10SiMg. The method for controlling quenching deformation of the die casting in this example includes the following steps:

[0057] Step S1: solution treatment and zone cooling

[0058] The longitudinal beam die casting was placed in a high-temperature furnace for solution treatment. The furnace temperature was set to 500°C and held for 4 hours. After the predetermined solution treatment time, the die casting was quenched and cooled in a zoned manner. The actual deformation of the die casting after cooling was measured. During the solution treatment and the entire quenching and cooling process, the casting was continuously restrained inward along the length of the casting. In this embodiment, the restraint was applied in the X direction along the length of the casting.

[0059] Zoning cooling includes dividing the surface area of the die casting and cooling different divided areas with cooling media of different parameters.

[0060] Specifically, the area with ribs or wall thickness greater than 3 mm is divided into the first area, and the area without ribs and wall thickness less than or equal to 3 mm is divided into the second area. Figure 1 As shown in FIG. 1 , the first region is cooled by a first medium, and the second region is cooled by a second medium. The heat transfer coefficient between the first medium and the first region is 1000 W / (m2·K), and the heat transfer coefficient between the second medium and the second region is 150 W / (m2·K).

[0061] In this embodiment, the first and second media are both air with different parameters. The heat transfer coefficient between the media and the die casting is controlled by adjusting the air flow rate or pressure. That is, the first medium is strong air and the second medium is weak air. Switching between strong and weak air can be achieved by adjusting the air flow rate or pressure of different nozzles.

[0062] Step S2: Establish a simulation model and perform a partitioned quenching and cooling simulation based on the parameters of step S1 to obtain a simulated deformation of the die casting.

[0063] Specifically, a simulation model was established, including the thermophysical parameters and thermoelastic stress data of Al10SiMg, as shown in Table 1. It was input into the finite element software, and the partition quenching cooling simulation was performed based on the parameters of step S1 and the longitudinal beam deformation was calculated to obtain the simulated deformation of the die casting, as shown in Table 1. Figure 3 shown.

[0064]

[0065] Step S3: Compare the simulated deformation with the actual deformation, and modify the model according to the comparison result to ensure that the difference between the simulated deformation and the actual deformation is less than or equal to 0.2 mm.

[0066] Specifically, if the difference between the simulated and actual deformations is less than or equal to 0.2 mm, the model meets the simulation accuracy requirements and no further correction is required. If the difference between the simulated and actual deformations is greater than 0.2 mm, the model needs to be further corrected until the difference is less than or equal to 0.2 mm. This correction step involves a second test of the data in Table 1, and then re-entering the updated data into the finite element software for simulation.

[0067] Step S4: Based on the modified model, the zoned quenching cooling process of the die casting is simulated and optimized, and after the simulation optimization, the difference in simulated cooling rate between different areas of the die casting is ensured to be within 5° C. / s.

[0068] Specifically, the simulation optimization optimizes the first region and the corresponding cooling medium. For regions where the area of the reinforcement ribs per unit projected area exceeds 10%, the heat transfer coefficient between the region and the cooling medium is 1500W / (㎡·K); for regions where the area of the reinforcement ribs per unit projected area is between 3% and 10%, the heat transfer coefficient between the region and the cooling medium is 800W / (㎡·K); and for regions where there are no reinforcement ribs or the area of the reinforcement ribs per unit projected area is less than 3%, the heat transfer coefficient between the region and the cooling medium is 300W / (㎡·K). The projection plane corresponding to the projection is perpendicular to the direction of the cooling medium ejection, that is, the direction of the projection light is the direction of the cooling medium ejection.

[0069] Step S5: Perform a quenching and cooling test on the die casting based on the partitioned quenching and cooling process after simulation optimization. Multiple thermocouples are set in each partition. The cooling rate of each area of the die casting is monitored based on the measurement results of the thermocouples. The partitioned quenching and cooling process is corrected based on the cooling rate results to ensure that the actual cooling rate difference between different areas of the die casting is within 5°C / s.

[0070] Overall, in this embodiment, five thermocouples are arranged at equal distances along the length direction of the die-casting side at the center positions of both sides of the die-casting in the first region, and are located within the first region; five thermocouples are arranged at equal distances along the X direction at the center positions of the upper and lower surfaces of the die-casting in the second region to achieve more accurate temperature monitoring.

[0071] Specifically, if the average difference in cooling rate between different regions is less than or equal to 5°C / s, the model meets the simulation accuracy requirements and no further correction is required. If the average difference in cooling rate between different regions is greater than 5°C / s, the model needs to be further corrected until the average difference in cooling rate between different regions is less than or equal to 5°C / s. The correction in this step involves a secondary test of the heat transfer coefficient with the die casting under different cooling medium parameters. After updating the data, re-enter the finite element software for simulation.

[0072] In this embodiment, the average cooling rates at the rib (first region) and the edge (second region) are measured to be 4°C / s and 6°C / s, respectively, and the average difference in cooling rates between the two is 2°C / s.

[0073] Step S6: Perform zone quenching and cooling on the die casting based on the corrected zone quenching and cooling process, and obtain the corrected deformation of the die casting after quenching and cooling. Compare the corrected deformation with the design dimension data of the die casting, and mark the position where the deformation degree is greater than 1 mm.

[0074] In this embodiment, the deformed dimensional data of the longitudinal beam based on the modified zone quenching and cooling process is compared with the target design dimensional data of the die casting. It is found that there are two locations where the casting has a large deformation after quenching, with deformation amounts of 1.1mm ( Figure 2 B in the middle) and 1.3mm ( Figure 2 A in the middle), such as Figure 2 shown.

[0075] Step S7: Based on the modified model of the zoned quenching and cooling process, a constraint simulation analysis is performed on the positions where the deformation degree is greater than 1 mm to obtain a constraint method with the minimum deformation degree.

[0076] The constraint simulation is to perform constraint simulation in the Y, Z, and YZ directions on positions A and B where the deformation degree is greater than 1 mm, and obtain the constraint method with the minimum deformation degree. The results are shown in Table 2.

[0077]

[0078] It can be seen from Table 2 that the deformation of the longitudinal beam corresponding to the constraint methods No. 1, 2, and 3 is relatively small.

[0079] Step S8: After the constraint simulation analysis, find the three constraint methods with the smallest deformation, and perform actual quenching and cooling of the die casting based on the three constraint methods with the smallest deformation and the partitioned quenching and cooling process corrected in step S5. The constraint method with the smallest deformation of the die casting and the corrected partitioned quenching and cooling process are selected as the optimal control method.

[0080] Although the corrected cooling process has been obtained in step S5 and the optimal constraint method has been obtained in step S7, there may still be certain error fluctuations, and actual experiments are needed to obtain the optimal control quenching process. The final results show that the longitudinal beam is constrained by the constraint method No. 3 in Table 2 and the corrected partitioned quenching cooling process in step S5 is used to quench the longitudinal beam. After complete cooling, the longitudinal beam is subjected to a dimensional scan. It is found that the maximum deformation of the longitudinal beam is controlled within 0.5mm, which is better than the constraint methods No. 1 and 2 in Table 2. The actual effect is better than the corresponding simulation results (maximum deformation within about 0.7mm). Figure 4 As shown, it is shown that the control method of this embodiment can effectively suppress the large deformation that may occur in the quenching process of the longitudinal beam, and the actual effect is better than the simulation effect.

[0081] The method for controlling quenching deformation of large thin-walled die castings of the present invention comprises the following steps: performing zone cooling on the die casting after solution treatment to obtain the actual deformation of the die casting after cooling; establishing a simulation model to obtain the simulated deformation of the die casting; comparing the simulated deformation with the actual deformation; simulating and optimizing the zone quenching cooling process of the die casting based on the revised model; performing a quenching cooling test on the die casting based on the simulated optimized zone quenching cooling process, and revising the zone quenching cooling process based on the cooling rate result; performing zone quenching cooling on the die casting based on the revised zone quenching cooling process, and obtaining the revised deformation of the die casting after quenching cooling, and comparing the revised deformation with the design dimension data of the die casting; performing constraint simulation analysis on positions with a deformation degree greater than 1 mm to obtain a constraint method with the minimum deformation degree, performing actual quenching cooling on the die casting based on the three constraint methods with the minimum deformation and the revised zone quenching cooling process, and selecting the constraint method with the minimum deformation of the die casting and the revised zone quenching cooling process as the optimal control method. The large thin-walled die-casting quenching deformation control method of the present invention can effectively control the deformation of large thin-walled die-castings, thereby reducing the subsequent manual shaping and processing costs, and can greatly improve the overall qualification rate of the casting blank size, providing reliable technical guarantee for improving the quality and efficiency of the production of large thin-walled die-castings.

[0082] The above-described embodiments, prepared by the methods of the present invention, are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the present invention and implement it accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent variations or modifications made in accordance with the spirit and substance of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A method for controlling quenching deformation of die castings, characterized in that: The steps include: The die castings after solution treatment are cooled in different zones, including the division of the surface area of the die castings and the use of cooling media with different parameters for different zones, and the actual deformation of the die castings after quenching and cooling is obtained; Establish a simulation model and perform partitioned quenching and cooling simulation to obtain the simulated deformation of the die casting; Comparing the simulated deformation with the actual deformation, and modifying the model according to the comparison result to ensure that the difference between the simulated deformation and the actual deformation is less than or equal to 0.2 mm; Based on the revised model, the zoned quenching cooling process of the die casting was simulated and optimized. After the simulation optimization, the difference in the simulated cooling rate between different areas of the die casting was ensured to be within 5°C / s. Based on the simulated and optimized partitioned quenching and cooling process, a quenching and cooling test was conducted on the die casting. Multiple thermocouples were set up in each partition. The cooling rate of each area of the die casting was monitored based on the thermocouple measurement results. The partitioned quenching and cooling process was modified based on the cooling rate results to ensure that the actual cooling rate difference between different areas of the die casting was within 5°C / s. Performing zone quenching and cooling on the die casting based on the revised zone quenching and cooling process, and obtaining a revised deformation of the die casting after quenching and cooling, comparing the revised deformation with the design dimensional data of the die casting, and marking locations where the deformation is greater than 1 mm; Based on the modified partitioned quenching and cooling process model, constraint simulation analysis was performed on locations where the deformation degree was greater than 1 mm, and the constraint method with the minimum deformation degree was obtained.

2. The control method according to claim 1, characterized in that: The surface areas of the die casting are divided into: the area with reinforcing ribs or the corresponding wall thickness greater than 3 mm is divided into the first area, and the area without reinforcing ribs and the corresponding wall thickness less than or equal to 3 mm is divided into the second area.

3. The control method according to claim 2, characterized in that: The cooling of the divided different areas using cooling media with different parameters is as follows: the first area is cooled by a first medium, and the second area is cooled by a second medium; the heat exchange coefficient between the first medium and the first area is 200-2000 W / (m2·K), and the heat exchange coefficient between the second medium and the second area is 100-200 W / (m2·K).

4. The control method according to claim 2, characterized in that: The simulation optimization of the zoned quenching cooling process of the die-cast part is as follows: the first area and the corresponding cooling medium are optimized, and the heat transfer coefficient between the area where the area of the reinforcing ribs accounts for more than 10% of the unit projected area and the cooling medium is 1000-2000W / (㎡·K); the heat transfer coefficient between the area where the area of the reinforcing ribs accounts for 3-10% of the unit projected area and the cooling medium is 600-1000W / (㎡·K); the heat transfer coefficient between the area where there are no reinforcing ribs or the area of the reinforcing ribs accounts for less than 3% of the unit projected area and the cooling medium is 200-600W / (㎡·K).

5. The control method according to claim 3, characterized in that: The first medium and / or the second medium is a fluid cooling medium, and the heat transfer coefficient between the cooling medium and the die casting is controlled by adjusting the fluid flow rate or pressure.

6. The control method according to claim 1, characterized in that: The model is corrected according to the comparison results as follows: if the difference between the simulated deformation and the actual deformation is less than or equal to 0.2 mm, the model meets the simulation accuracy requirements and no further correction is required; if the difference between the simulated deformation and the actual deformation is greater than 0.2 mm, the model needs to be further corrected until the difference between the two is less than or equal to 0.2 mm.

7. The control method according to claim 1, characterized in that: The partitioned quenching cooling process is corrected based on the cooling rate results as follows: if the average difference in cooling rate between different regions is less than or equal to 5°C / s, the model meets the simulation accuracy requirements and no further correction is required; if the average difference in cooling rate between different regions is greater than 5°C / s, the model needs to be further corrected until the average difference in cooling rate between different regions is less than or equal to 5°C / s.

8. The control method according to claim 1, characterized in that: The average difference in cooling rate between different regions of the die casting is within 2°C / s.

9. The control method according to claim 1, characterized in that: The constraint simulation is to perform constraint simulation in the Y, Z and YZ directions on positions where the deformation degree is greater than 1 mm.

10. The control method according to any one of claims 1 to 9, characterized in that: The steps also include: finding three constraint methods with the smallest deformation after constraint simulation analysis, and conducting quenching and cooling tests based on the three constraint methods with the smallest deformation and the revised partitioned quenching and cooling process, and selecting the constraint method with the smallest deformation of the die casting and the revised partitioned quenching and cooling process as the optimal control method.

11. The control method according to claim 1, characterized in that: The solution treatment is to keep the die casting at 480-530° C. for 1-6 hours.

12. The control method according to claim 1, characterized in that: During the solution treatment and quenching cooling process, the die casting is continuously constrained at both ends of the length direction of the die casting, and the constraint direction is inward along the length direction of the die casting.

13. A method for preparing a die casting, characterized in that: The method comprises the steps of the method for controlling quenching deformation of a die casting as described in any one of claims 1 to 12.

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